Server software is sometimes used for document conversions. As an example, a RightFax server that was commercialized by the assignee of the present patent application converted documents from a native document format to a facsimile document format. A native document format is a document format that is associated with an application (“native application”). Examples of native document formats and corresponding native applications are DOC files and Microsoft® Word®, Workbooks and Microsoft® Excel®, hypertext markup language documents and an Internet browser, and so forth.
Some of these native applications supported an interface called automation, which is also known as object linking and embedding (“OLE”) automation. The server software could command these applications using their OLE automation interfaces to open a document and print the document. When printing the document, a printer driver can be specified, such as to print the document in a common document format. Examples of common document formats include Adobe@ Portable Document Format, Hewlett Packard@ Printer Control Language, facsimile or Tagged Image File Format (“TIFF”), and Adobe@ PostScript®. Using the RightFax server, for example, a user could provide a native document format file for sending via facsimile. The RightFax server would receive the document, employ the native application to convert the document to a TIFF common document format, and send the converted TIFF formatted document via facsimile services.
Document conversion server software, such as the RightFax server, is designed to function in high-volume or high-use environments, and can receive and convert many documents from many users. When the server software receives multiple documents, it conventionally would create multiple instances of the automated native application to convert several documents concurrently. However, the native applications are generally designed for use by a single user at a time. When multiple instances of the native applications are launched concurrently, they sometimes behave unexpectedly, such as by freezing or crashing (e.g., because of memory leaks, prompts for user input, and so forth). Oftentimes, the native applications would freeze or crash for various unknown reasons. When this occurs, the document conversion server software can also freeze or crash, such as when the document conversion server software and the native application operate in the same process space.
Other technology exists for converting documents from a native document format to a common document format. The document conversion server software could employ this technology. However, this technology commonly does not support all features of the native applications and so the resulting conversion often does not provide adequate fidelity. As an example, when this technology receives a Word® document containing an embedded Microsoft® Excel® chart or spreadsheet, the technology may not produce output that is similar to what the native application (e.g., Microsoft® Word® in this case) would produce.